In the production and process of tobacco products including aging, blending, sheet forming, cutting, drying, cooling, screening, shaping and packaging, considerable amounts of by-products including tobacco fines, stems, and other small tobacco plant parts are produced. Those skilled in the art recognize that such by-products can be combined with binder to form a coherent sheet which resembles leaf tobacco and which sheet is commonly referred to as reconstituted tobacco.
There are basically two commonly but quite different commercially employed processes used for the preparation of reconstituted tobacco.
One procedure, referred to commonly as band casting, employs a slurry of finely divided tobacco parts and a binder which is coated onto a steel band and then dried. After drying, the sheet is shredded and used in various tobacco products including as a cigarette filler.
Waste or scrap tobacco parts or dust are normally bound together by providing an adhesive to give the tobacco sheet coherence. Various adhesives or binding agents have been used or proposed for this purpose, many of them being modified cellulose or other non-tobacco derivatives. Improvements in binding agents have led to the use of adhesive material derived from tobacco, notably, tobacco pectins. Such processes are taught in various U.S. patents including U.S. Pat. Nos. 3,353,541; 3,420,241; 3,386,449; 3,760,815 and 4,674,519. Reconstituted tobacco made in the hereinabove mentioned patents is obtained by including a pectin release step in the sheet forming process. The disclosures of the foregoing patents and any patent or literature disclosure noted hereinbelow are expressly incorporated herein by reference.
In the '541, '241 and '449 patents, diammonium phosphate or ammonium orthophosphate is employed in the release of pectins from the tobacco by-products. The '815 patent discloses the use of ammonium salts to release binder from the tobacco by-product.
The second known process employs papermaking techniques. Examples of patents which disclose such reconstituted tobacco processes include U.S. Pat. Nos. 3,428,053; 3,415,253; 3,561,451; 3,467,109; 3,483,874; 3,860,012 and 3,847,164.
In the papermaking process, the soluble ingredients of natural tobacco are extracted. The tobacco may be macerated or comminuted in preparation for extraction. The extraction is normally performed by use of water. The extract is separated, and the insoluble fibers with or without additives are transformed into a self-sustaining web by the usual papermaking technique. The tobacco extract, which may be concentrated to a liquor, is then reapplied into the web. The application of the extracted tobacco material may be achieved in any appropriate manner, as by spraying, saturating, or otherwise.
In the past, materials have been added to the concentrated extract and there has been some limited success with ammonium salts in order to reduce smoke irritation and to form flavor precursors from sugar-ammonia reaction products.
There remains, however, a continuing need for further improvement in tobacco smoke quality and in reducing smoke irritation. Furthermore, there remains a continuing need to obtain an improved papermaking process for the preparation of reconstituted tobacco sheet in which the extraction of natural water soluble materials from the tobacco furnish is enhanced.
It is an object of the present invention to provide a process for the preparation of reconstituted tobacco sheet using the papermaking process in which some of the water insoluble tobacco biopolymers are converted into water soluble materials. Thus, there is an enhanced aqueous extraction of the newly formed solubles as well as solubles indigenous to tobacco.
It is a further object of the present invention to provide a reconstituted tobacco sheet having improved smoke quality.